Diapers could soon be a bit cheaper for parents in D.C.

Mayor Muriel Bowser announced this week that she will fund a 2016 bill passed by the D.C. Council that exempts diapers — for both kids and adults — from the city’s 6 percent sales tax. A separate portion of that bill exempting feminine hygiene products like tampons and pads from the sales tax was funded in last year’s budget.

Advocates say exempting diapers from the sales tax can help low-income families save money; on average, families can spend upwards of $500 a year on diapers.

“Children require at least 50 diaper changes per week, or 200 diaper changes per month. By reducing the sales tax, families can buy 2 additional diapers for every percentage point reduction in the sales tax for the same money they would have used to buy 200 diapers with tax,” says the National Diaper Bank Network on its website. (We recently profiled the Greater D.C. Diaper Bank, whose founder testified in support of the Council’s 2016 bill.)

Bowser, who became a mother last year, made that point earlier this month during her State of the District Address.

“Those diaper costs add up, don’t they? Eliminating the diaper tax is one more way we can make it more affordable to raise children right here in D.C. — one pack of diapers at a time,” she said.

Only a small number of states currently offer an exemption for diapers, including Massachusetts, Minnesota, Pennsylvania, New Jersey, New York, Rhode Island and Vermont. California and Florida have both recently considered following suit. Locally, Maryland considers adult diapers a medical product and exempts them from the sales tax, but not diapers for children. And today Virginia Gov. Ralph Northam signed a bill that doesn’t eliminate the sales tax for feminine hygiene products, but reduces it to 2.5 percent from the current six percent.

Exempting diapers from D.C.’s sales tax is expected to cost the city $4.5 million in lost revenue a year. Provided the Council doesn’t remove the money from Bowser’s budget proposal, the exemption would kick in on Oct. 1.

This story originally appeared at WAMU. It has been updated.